A cellular network is a radio network distributed over land areas called cells, each cell served by at least one fixed-location transceiver known as a cell site or base station. When joined together these cells provide radio coverage over a wide geographic area. This enables a large number of portable transceivers (e.g., mobile phones, pagers, etc.) to communicate with each other and with fixed transceivers and telephones anywhere in the network, via base stations, even if some of the transceivers are moving through more than one cell during transmission.
The 3rd Generation Partnership Project® (“3GPP”) LTE provides a standard in the mobile network technology tree that produced the Global System for Mobile Communications with Enhanced Data rates for GSM Evolution (“GSM/EDGE”) and UMTS/HSPA (“High Speed Packet Access”) network technologies. It is a project of the 3GPP, operating under a name trademarked by one of the associations within the partnership, the European Telecommunications Standards Institute. LTE Advanced (“LTE-A”), a fourth generation standard (“4G”) of radio technologies, is designed to increase the capacity and speed of mobile telephone networks. LTE Advanced is backwards compatible with LTE and uses the same frequency bands, while LTE is not backwards compatible with third generation (“3G”) standards.
A frequency domain equalizer (“FDE”) receiver is used in LTE. It can also be used in a multi-mode receiver supporting both LTE and UMTS. However, in an FDE receiver, performance degrades, particularly in an equal taps channel where the channel has a frequency null. Usually a decision feedback equalizer (“DFE”) is used to improve receiver performance. However, this problem is unresolved in a multi-mode receiver. Because of the use of a spreading factor in UMTS systems that is employed to convert symbols into chips, decision feedback for a detected symbol cannot be applied as straightforwardly as in LTE systems. Thus, what is needed in the art is an efficient receiver structure that can be used for both LTE and UMTS systems.